A third accuser has come forward claiming he had sexual relations with Elmo puppeteer Kevin Clash while underage.

The man, identified in court papers only as "D.O.," claims he began the physical relationship in 2000, when he was 16. In court papers filed Tuesday in New York City, he claims he met and spoke with Clash on a gay telephone chat line, and several days later visited Clash's New York apartment.

This marks the third time in two weeks that allegations of engaging in underage sex have been leveled against Clash, a Baltimore County native who rose to fame as the voice of the child-like Elmo, a fixture on the PBS series "Sesame Street."

"He had been thinking he was not going to come forward," Jeff Herman, the latest accuser's Miami-based attorney, told The Baltimore Sun. "But after seeing the first two victims being challenged, he decided that he needed to come forward to validate their claims, because the same thing happened to him."

"The federal cases filed against Kevin Clash are without merit," Berger said in an emailed statement. "The cases and Mr. Clash's reputation will be defended vigorously."

Herman said his client, who according to court papers lives in Florida, visited Clash's apartment again in 2003 and 2004, when he was no longer underage. The suit, which charges that Clash "trolled gay telephone chat line rooms to meet and have sex with underage boys," seeks unspecified damages.

His client "wanted to make the point that this is not about [getting] money from him," Herman said. "This is about justice and seeking the truth."

The attorney said his client began writing a book including details of the relationship in 2009. Pages from it were released during a Tuesday afternoon news conference in New York.

In a chapter from the manuscript entitled "Tickled My Heart," D.O. talks about meeting a "Mr. Tickler" in the older man's New York apartment and engaging in sexual activity.

Clash, a Baltimore County native who was the voice of Elmo for more than a quarter-century, left the show Nov. 20 after two charges that he had had sex with minors. The first arose a week earlier but was recanted two days later by the accuser, identified in media reports as Sheldon Stevens, a model/actor who lives in Pennsylvania. Stevens has since said he regretted recanting the accusation, according to news reports.

The second accuser, New York native Cecil Singleton, leveled a similar accusation against Clash a week later. Singleton, who said he was 15 at the time of his encounter with Clash in 2003, has filed a lawsuit against Clash, seeking $5 million in damages. He is also being represented by Herman.

Herman said he was approached by "D.O." after the second set of allegations against Clash came to light. The attorney said he has been approached by others making similar claims.

"I've been contacted," he said, declining to elaborate. "These are just allegations that I'm investigating."

Clash, 52, admitted having a sexual relationship with the first accuser, but said it did not involve underage sex. Following his resignation, he released a statement saying, "I am resigning from Sesame Workshop with a very heavy heart. I have loved every day of my 28 years working for this exceptional organization. Personal matters have diverted attention away from the important work Sesame Street is doing and I cannot allow it to go on any longer. I am deeply sorry to be leaving and am looking forward to resolving these personal matters privately."

Sesame Workshop, the producers of "Sesame Street," has said Elmo will continue as a character on the show.